Light has been used to create color intensity for displays, but the methods and the systems used are inefficient, bulky, and produce dim or non-scalable results. State of the art laser imaging displays have used lasers as intense color beams by utilizing various beam scanning apparatuses. In the case of lasers, display pixel output is generated from a combination of three beams of light: red, green, and blue. The three beams of light can be combined at various intensities to produce a particular color depth, intensity, and saturation.
In particular, the semiconductor laser has become important component of imaging system applications as the size, weight and power requirements of the semiconductor laser have decreased over time with its continued utilization. Semiconductor lasers have been used as the light sources for displays by delineating the light from the light sources into highly resolved intensity profiles which are used to create pixels. However, some existing techniques require the use of an analog power source variation while others rely on the use of timing and/or mechanical reflection means. The use of lasers as a light source also has the drawback of a scintillation effect, which produces light and dark areas of the spot or pixel.
Producing correct color semiconductor laser sources has only been possible with edge emitting semiconductor laser devices. However, this type of laser device is not conducive to photo-lithographically arrayed designs since they must be cleaved on edge to produce the cavity for lasing. Generally, the substrate is cleaved after fabrication. Consequently, this has limited laser display sources to single devices or mechanically ganged single devices.
The vertical-cavity surface-emitting laser (VCSEL) is a type of semiconductor laser diode with laser beam emission perpendicular from the top surface. In contrast, conventional edge-emitting semiconductor lasers emit from surfaces formed by cleaving the individual chip out of a wafer. While VCSELs offer advantages over edge-emitting lasers, VCSELs have not found use in imaging systems because VCSELs have only recently been created that are capable of producing the green output wavelength. While green output VCSELs have been created, these devices had extreme power requirements and a number of reliability issues. Materials research necessary to create other VCSELs capable of generating a better green output, as well as other color outputs, has progressed slowly. In fact, the blue VCSEL has only been commercially available for a few years.
VCSELs with external cavities (VECSELs) are a type of VCSELs that have been reconfigured to have the cavity extended outside of the wafer. VECSELs are optically pumped with conventional laser diodes. In addition, optical elements, such as non-linear crystals, can be used for doubling the frequency of the light and for allowing colored light output using the materials best suited for semiconductor laser fabrication.
Devices that use VECSELs, for frequency doubling output, in displays are designed to produce light sources in three distinct colors. This is in contrast to display devices, such as projectors, that use white light sources which are filtered to generate a particular color. Arrays of VECSEL devices are used to produce a single, bright, colored light source. The single colored light source is typically static, meaning that the intensity of the light source does not change. However, it is known that a mirror can be positioned among a plurality of mirrors to determine the color intensity at a point. Other known and related techniques include pulsing of the single light source or timing the light source to change intensity values. However, all of these methods are heavily dependent on mechanical mirrors. This technology is generally termed Digital Light Processor (DLP) technology.
DLP technology has dominated high quality display for a number of years. DLP technology is widely used in projection displays, along with many other different types of displays. DLP uses an array of Micro-electromechanical (MEM) devices as multiple tiny reflectors which can be modulated by electrical signals which reflect a specific amount of a colored light producing a combined color from 3 multiple color sources. These sources are generally colors filtered out of a white light source such as a costly projector lamp that uses a great amount of wasted energy that is not in the filtered wavelength. All this excess wasted energy produces large amounts of heat which make the system size much larger and more expensive in order to manage the thermal problem created by the excess heat.
VCSEL arrays have been arrayed and individually addressable for the purposes of parallel optical scanning and data transmission. Matrix addressable VCSELs have been previously used for imaging and data transmission, but are configured to use the devices in separately controllable means forming many individual devices driven independently. There have been other concepts suggested that use these separately controlled devices in an array to produce an image by varying the power source of each device to produce an intensity.
A summation of present techniques shows laser color formation for displays to be generated by adjusting the current source to make brighter or dimmer color intensities forming the pixel, or using laser arrays to produce a color source and reflecting or timing and scanning that source to produce the final intensity. All of these technologies require expensive, bulky, energy wasting technology and/or rely on mechanical mirrors, arrays of mirrors, and expensive supporting apparatuses to function.